The invention relates to a fuel return valve, which comprises a housing and a closing unit, a first passage, which is line-connected to a fuel pump, a second passage, which is line-connected to an internal combustion engine, and a third passage, which is line-connected to the fuel tank, as well as a pressure chamber, being formed in the housing, which pressure chamber is in communication with the first passage, and, via the closing unit, with the third passage, which closing unit is acted on by a spring accommodated in a housing attachment.
Fuel return valves are used in the fuel supply system of motor vehicles. They are arranged in the fuel feed and serve the purpose firstly of returning surplus fuel to the fuel tank to achieve low fuel consumption in the engine, and secondly of preventing the feed line from emptying out when the engine is switched off.
A fuel return valve of the conventional design is described, for example, in Automobiltechnischen Handbuch [Handbook of Automotive Engineering] (supplement volume to the 18th edition, page 263), published by Verlag Walter de Gruyter. In this valve, the closing unit is a diaphragm inserted in a sealing manner between the housing and the housing attachment and having a small valve plate which only opens up a small throughflow opening. In other embodiments, a ball is also used instead of the valve plate. To adjust the spring force acting on the valve plate, the space which contains the spring in the housing attachment is in communication either with atmosphere or with a reduced-pressure source, for example the induction pipe of the internal combustion engine. This external connection therefore requires the use of the diaphragm which is inserted in a sealed manner. This design is complex and expensive to produce, and furthermore the diaphragm is a wearing part.
Therefore, it is an object of the invention to create a fuel return valve which is maintenance-free, simple and inexpensive to produce, yet nevertheless satisfies all functional requirements.